/* *****************************************************************
    MESQUITE -- The Mesh Quality Improvement Toolkit

    Copyright 2010 Sandia National Laboratories.  Developed at the
    University of Wisconsin--Madison under SNL contract number
    624796.  The U.S. Government and the University of Wisconsin
    retain certain rights to this software.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    (lgpl.txt) along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    (2010) kraftche@cae.wisc.edu

  ***************************************************************** */

/** \file TRel2DUntangle.cpp
 *  \brief
 *  \author Jason Kraftcheck
 */

#include "Mesquite.hpp"
#include "TUntangleMu.hpp"
#include "MsqMatrix.hpp"
#include "TMPDerivs.hpp"
#include "TMPCommon.hpp"
#include "MsqError.hpp"

namespace MBMesquite
{

TUntangleMu::~TUntangleMu() {}

std::string TUntangleMu::get_name() const
{
    return "untangle(" + mBaseMetric->get_name() + ")";
}

template < unsigned DIM >
inline bool TUntangleMu::eval( const MsqMatrix< DIM, DIM >& T, double& result, MsqError& err )
{
    bool valid = mBaseMetric->evaluate( T, result, err );
    if( MSQ_CHKERR( err ) || !valid ) return false;

    const double d = mConstant - result;
    const double s = fabs( d ) - d;
    result         = 0.125 * s * s * s;
    return true;
}

template < unsigned DIM >
inline bool TUntangleMu::grad( const MsqMatrix< DIM, DIM >& T,
                               double& result,
                               MsqMatrix< DIM, DIM >& deriv_wrt_T,
                               MsqError& err )
{
    bool valid = mBaseMetric->evaluate_with_grad( T, result, deriv_wrt_T, err );
    if( MSQ_CHKERR( err ) || !valid ) return false;

    if( mConstant < result )
    {
        const double s = result - mConstant;
        result         = s * s * s;
        deriv_wrt_T *= 3 * s * s;
    }
    else
    {
        result      = 0;
        deriv_wrt_T = MsqMatrix< DIM, DIM >( 0.0 );
    }

    return true;
}

template < unsigned DIM >
inline bool TUntangleMu::hess( const MsqMatrix< DIM, DIM >& T,
                               double& result,
                               MsqMatrix< DIM, DIM >& deriv_wrt_T,
                               MsqMatrix< DIM, DIM >* second_wrt_T,
                               MsqError& err )
{
    bool valid = mBaseMetric->evaluate_with_hess( T, result, deriv_wrt_T, second_wrt_T, err );
    if( MSQ_CHKERR( err ) || !valid ) return false;

    if( mConstant < result )
    {
        const double s = result - mConstant;
        result         = s * s * s;
        hess_scale( second_wrt_T, 3 * s * s );
        pluseq_scaled_outer_product( second_wrt_T, 6 * s, deriv_wrt_T );
        deriv_wrt_T *= 3 * s * s;
    }
    else
    {
        result      = 0;
        deriv_wrt_T = MsqMatrix< DIM, DIM >( 0.0 );
        set_scaled_I( second_wrt_T, 0.0 );  // zero everything
    }

    return true;
}

TMP_T_TEMPL_IMPL_COMMON_ERR( TUntangleMu )

}  // namespace MBMesquite
